Lateral pectoral nerve

The lateral pectoral nerve originates from the lateral cord of the brachial plexus, receiving contributions from the C5, C6, and C7 spinal nerve roots. Its designation as "lateral" comes from its origin in the lateral cord. After arising from the lateral cord, just inferior to the clavicle, it courses inferomedially, travelling parallel to the thoracoacromial vessels, and ends up innervting the upper portions of the pectoralis major muscle.

The lateral pectoral nerve may have an articular branch that contributes to the innervation of the shoulder joint.

Conversely, the medial pectoral nerve arises from the medial cord of the brachial plexus, with fibers primarily derived from spinal nerve roots C8 and T1. Its designation as “medial” comes from its origin in the medial cord. It typically passes through or around the lower border of the pectoralis minor muscle before reaching and innervating both the pectoralis minor and the lower portions of the pectoralis major muscle.

An anastomosis, called the "ansa pectoralis," can occur between the lateral and medial pectoral nerves, contributing further to the innervation of the pectoral muscles.